This invention relates to power supplies for electroluminescent (EL) panels, and more particularly to power supplies which effectively are inhibited or blocked and thus shut down in the event of a short in the panel circuit or a panel failure. The application is further directed to particular power supplies for such panels including a transformerless power supply.
The use of electroluminescent panels, particularly in the automotive and aircraft field, has required the development of DC operated power supplies for such panels, which can conveniently take a low voltage source of DC power available, and provide an operating voltage for the electroluminescent panels involved. For example, EL panels have come into widespread use in light aircraft having only a DC power system, for enunciator panels or for other illumination devices, and in automobiles as a design feature such as for opera lights, or for backlighting of radio controls or the like. There has accordingly arisen a need for low cost, lightweight and dependable power supplies which can operate on a low voltage direct current source, such as 12 volts DC, and provide dependable power for the electroluminescent lamp or panel.
A further requirement has been that of providing a power supply which is blocked or inhibited and is thus failsafe on the occurrence of an electrical or mechanical malfunction in the panel itself, causing the panel to short. Shorting of the EL panel may result by reason of improper construction of the panel itself or mechanical abuse or catastrophic failures. In the past, such shorting has tended to place an uncommonly high load upon the inverter power supply, to the point where the power supply may fail, and in failing, may cause an electrical hazard, such as an overload, or a source of localized heating, which can under certain circumstances cause a fire hazard.
There is further a need for dependable EL power supplies which are lightweight, and which can be made in a highly compact form, at relatively low cost. For example, there is a need for a power supply which can be formed entirely on a printed circuit board or on an EL lamp itself, and thus there is a requirement for a power supply which is transformerless and made up entirely of solid state low profile elements.